Abstract: In order to study coal deformation law of hydraulic flushing passing through layer to guide Xuehu Coal Mine to control gas outburst, based on the field test, we use FLAC^3D software and related theories to study numerical simulation of stress field distribution and displacement field distribution of coal around punching hole, and analyze the influence of the amount of coal on the stress and displacement of the surrounding coal and conduct the field test. We get a series of results, for example, when the amount of coal is up to 1.54 t/m, hydraulic punching makes coal pressure relief around the hole, and the range of the reduction of maximum principal is 2.26 m to 3 m. The tensile stress occurs on the top plate of the hole, coal around the hole forms radial displacement which is point to hole, the range of coal displacement is positively related with the amount of coal, and the range of which is 2.3 m to 3.18 m, and the displacement of the central part of the hydraulic punching is bigger than the bottom. Combined with gas extraction effect, we make comprehensive analysis and comparison to determine that the coal amount of about 1.15 t/m is the reasonable amount of coal in Xuehu Coal Mine.